Phospholipid fatty acids in forest soil four years after organic matter removal and soil compaction

Disturbance caused by forest management practices can have a striking effect on soil microbial activity in a forest ecosystem. Phospholipid fatty acid (PLFA) profiles were developed and compared for soils in plots of a harvested forest stand 4 years after removing only merchantable logs (130) and removing the whole tree plus forest floor (WT+FF), in combination with two levels of soil compaction (none and severe) and plots in an uncut forest stand (control). Soils in both forest stands were characterized by a cherty residuum that is primarily of the Clarksville series (Loamy-skeletal, mixed, mesic Typic Paleudults). Thirty soil samples were collected from 0 to 10 cm depth from each plot and pooled; a composite sample of the mixture was analyzed for each of the 15 plots. After 4 years, PLEA representing bacterial biomass did not differ significantly (P > 0.05) between treated and control plots. Prokaryote organisms outnumbered polyonic organisms by 5 to 1. Among structure groups, unsaturated and saturated differed significantly between treatments, but branched, cyclopropane, and polyenoic did not. Individual fatty acids differed between treatments regardless of significant differences between structure groups. Both cell membrane permeability and turnover rate were lower for organisms in control plots than for organisms in treated plots. Differences in fatty acid profiles attributed to soil disturbance suggest that attributes of soil disturbance favors specific groups of organisms over others. Further work is needed to identify how forest soil processes influenced by disturbance impact microbial community structure and growth to determine if microbial activity as inferred by PFLA analysis can be used to monitor the recovery of soils in forested sites. (C) 2002 Elsevier Science B.V. All rights reserved.